Visual prediction of collision with natural and nonnatural motion functions

A movement with constant velocity looks fast in the beginning and later slows down, whereas a certain type of accelerated motion (natural motion) looks constant throughout. It was predicted that early occlusion of a constant motion would lead to overestimation of velocity whereas late occlusion would not. With natural motion, there would be no such difference. Constant and natural motions together with constant deceleration and constant acceleration motions were tested in a modified prediction-of-collision experiment. The results agree well with the predictions. It was concluded that the phenomena previously found are operative also in a more complex perceptual task where the observer’s attention is not focused on velocity directly. The visual system seems to achieve perception of partly occluded motion by applying a natural motion function rather than constant velocity. Acquaintance with the phenomena does not seem to alter the way they are perceived.